Evaluating Drug Resistant Mutations to HCV NS3 Protease Inhibitors in Iranian Naïve Patients

International Journal of Peptide Research and Therapeutics - Hepatitis C virus (HCV) is an important causative agent of acute and chronic hepatitis. The non-structural protein 3 (NS3) of HCV...     

Interaction between hepatitis C virus proteins and host cell factors

Since the discovery of the hepatitis C virus (HCV) as the causative agent of non-A, non-B hepatitis, significant effort has been devoted to understanding this important pathogen. Despite the difficulty in culturing this virus efficiently, much is known about the organization of the viral genome and the functions of many of the viral proteins. Through the use of surrogate expression systems combined with cellular fractionation, pull-down experiments and yeast two-hybrid screens, numerous interactions between hepatitis C virus proteins and cellular components have been identified. The relevance of many of these interactions to hepatitis C biology remains to be demonstrated. This review discusses recent developments in this area of HCV research.     

Hepatitis C--new developments in the studies of the viral life cycle

Hepatitis C virus (HCV) is a causative agent of chronic liver disease leading to cirrhosis, liver failure and hepatocellular carcinoma. The prevalence of HCV is estimated as 3% of the world population and the virus is a major public health problem all over the world. For over 16 years, since HCV had been discovered, studies of the mechanisms of the viral life cycle and virus-host interactions have been hampered by the lack of a cell culture system allowing the virus to be grown in laboratory conditions. However, in recent years some new model systems to study HCV have been developed. The major breakthrough of the last two years was the cell culture system for maintaining the virus in an adapted hepatocyte-derived cell line. This review describes the techniques and applications of most of the in vitro systems and animal models currently used for working with hepatitis C virus.     

Synergy of small molecular inhibitors of hepatitis C virus replication directed at multiple viral targets

Chronic hepatitis C virus (HCV) infection is a significant worldwide health problem with limited therapeutic options. A number of novel, small molecular inhibitors of HCV replication are now entering early clinical trials in humans. Resistance to small molecular inhibitors is likely to be a significant hurdle to their use in patients. A systematic assessment of combinations of interferon and/or novel anti-hepatitis C virus agents from several different mechanistic classes was performed in vitro. Combinations of inhibitors with different mechanisms of action consistently demonstrated more synergy than did compounds with similar mechanisms of action. These results suggest that combinations of inhibitors with different mechanisms of action should be prioritized for assessment in clinical trials for chronic hepatitis C virus infection.     

The hepatitis C virus internal ribosome-entry site: a new target for antiviral research

The hepatitis C virus (HCV) is the main causative agent of non-A, non-B hepatitis in humans and a major cause of mortality and morbidity in the world. Currently there is no effective treatment available for the infection caused by this virus, whose replication depends on an unusual translation-initiation mechanism. The viral RNA contains an internal ribosome-entry site (IRES) that is recognized specifically by the small ribosomal subunit and by eukaryotic initiation factor 3, and these interactions allow cap (7-methyl-guanine nucleotide)-independent initiation of viral protein synthesis. In this article, we review the structure and mechanism of translation initiation of the HCV IRES, and its potential as a target for novel antivirals.     

IFITMs Restrict the Replication of Multiple Pathogenic Viruses

The interferon-inducible transmembrane protein (IFITM) family inhibits a growing number of pathogenic viruses, among them influenza A virus, dengue virus, hepatitis C virus, and Ebola virus. This review covers recent developments in our understanding of the IFITM's molecular determinants, potential mechanisms of action, and impact on pathogenesis.     

Establishment of Hepatitis C Virus RNA-Replicating Cell Lines Possessing Ribavirin-Resistant Phenotype

BackgroundRibavirin (RBV) is a potential partner of interferon-based therapy and recently approved therapy using direct acting antivirals for patients with chronic hepatitis C. However, the precise mechanisms underlying RBV action against hepatitis C virus (HCV) replication are not yet understood. To clarify this point, we attempted to develop RBV-resistant cells from RBV-sensitive HCV RNA-replicating cells.Conclusions/SignificanceThese newly established HCV RNA-replicating cell lines should become useful tools for further understanding the anti-HCV mechanisms of RBV.     

E2 of hepatitis C virus inhibits apoptosis

Hepatitis C virus (HCV) is the major causative agent of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma, and can be involved in very long chronic infections up to 30 years or more. Therefore, it has been speculated that HCV possesses mechanisms capable of modulating host defense systems such as innate and adaptive immunity. To investigate this virus-host interaction, we generated HCV replicons containing various HCV structural proteins and then analyzed the sensitivity of replicon-containing cells to the apoptosis-inducing agent, TRAIL. TRAIL-induced apoptosis was monitored by cleavage of procaspase-3 and procaspase-9 as well as that of their substrate poly(ADP-ribose) polymerase. TRAIL-induced apoptosis was inhibited in cells expressing HCV E2. Moreover, expression of HCV E2 enhanced the colony forming efficiency of replicon-containing cells by 25-fold. Blockage of apoptosis by E2 seems to be related to inhibition of TRAIL-induced cytochrome c release from the mitochondria. Based on these results, we propose that E2 augments persistent HCV infection by blocking host-induced apoptosis of infected cells.     

Antiviral activity of interferon-alpha against hepatitis B virus can be studied in non-hepatic cells and Is independent of MxA.

It is well established that interferon-alpha can induce non-cytotoxic intracellular suppression of hepatitis B virus replication, but the mechanisms involved are unclear. Cell culture studies to characterize these mechanisms are restricted, in part because hepatitis B virus replicates almost exclusively in liver-derived cells. To overcome this limitation we used a cytomegalovirus promoter-controlled hepatitis B virus expression system, which leads to intracellular viral replication even in non-hepatic cell lines. In this experimental system interferon-alpha treatment specifically suppressed viral replication demonstrating that antiviral activities against hepatitis B virus are not restricted to hepatic cells. Furthermore, the interferon-inducible MxA protein was recently reported to play a key role in the antiviral action of interferon-alpha against hepatitis B virus. Our data demonstrate that interferon-alpha also suppresses hepatitis B virus replication in MxA-deficient HEp2 cells, indicating that MxA is not essential for these activities. Taken together, our data imply that the experimental approach presented can also be adapted to established cell lines which are deficient in parts of the signal transduction pathway or other elements located further downstream, providing important insights into mechanisms specifically suppressing hepatitis B virus.     

Humoral immune response against hepatitis C virus

Antibodies are in several instances a reliable marker indicating vigorous immune response against infectious agents and in several viral diseases presence in the blood of specific anti-viral antibodies indicates an effective protection. However, this is not always true. For example, in the case of hepatitis C virus (HCV) an important human pathogen considered the causative agent of the nonA- nonB hepatitis, in spite of an intense antibody response there is no protection against a new infection and in the majority of infected individuals the virus overcomes host defences establishing a persistent infection. Here we describe how the dissection of the humoral immune response against HCV glycoprotein E2 of infected patients was useful for a better comprehension of the virus-host interplay. Cross-reactive antibodies directed against E2 are produced by the HCV-infected patient, but not all of them are protective, and some could even result to be detrimental for the patient. The cross-reactive anti-HCV/E2 humoral antibody response is complex and not necessarily completely beneficial to the host.     

Mapping of linear B cell epitopes on open reading frames 2- and 3-encoded proteins of hepatitis E virus using synthetic peptides

Abstract Hepatitis E virus (HEV) is the causative agent of non-A, non-B hepatitis which is transmitted by the fecal-oral route and occurs principally in the form of large epidemics and outbreaks in developing countries. Two overlapping synthetic peptides corresponding to overlapping DNA sequences of the ORF 3 of HEV genome were found to be immunoreactive with sera from patients involved in two epidemics of enterically transmitted non-A, non-B hepatitis. The results suggested the existence of two distinct epitopes. The four synthetic peptides representing these two epitopes from Burma and Mexico strains of hepatitis E virus, were used to investigate anti-HEV reactivities. HEV antibodies were detected in 84–88% of HEV-infected individuals according to the peptide used. The results suggest that a peptide-based ELISA can provide an accurate tool for the diagnosis of acute hepatitis type E.     

Pestivirus

Members of the genus Pestivirus, are causative agents of economically important diseases for livestock and wild animals that occur worldwide, such as bovine viral diarrhea, classical swine fever, and border disease of sheep. Pestivirus have novel insertions of host genes in the viral genome and functions of unique viral proteins, N(pro) and E(rns), related to the pathogenicity although genomic structure is closely related to the other viruses of Flaviviridae family, especially hepatitis C virus. In this review, recent studies on the molecular basis of pathogenicity of pestivirus infections were summarized.     

The lipid droplet is an important organelle for hepatitis C virus production

The lipid droplet (LD) is an organelle that is used for the storage of neutral lipids. It dynamically moves through the cytoplasm, interacting with other organelles, including the endoplasmic reticulum (ER). These interactions are thought to facilitate the transport of lipids and proteins to other organelles. The hepatitis C virus (HCV) is a causative agent of chronic liver diseases. HCV capsid protein (Core) associates with the LD, envelope proteins E1 and E2 reside in the ER lumen, and the viral replicase is assumed to localize on ER-derived membranes. How and where HCV particles are assembled, however, is poorly understood. Here, we show that the LD is involved in the production of infectious virus particles. We demonstrate that Core recruits nonstructural (NS) proteins and replication complexes to LD-associated membranes, and that this recruitment is critical for producing infectious viruses. Furthermore, virus particles were observed in close proximity to LDs, indicating that some steps of virus assembly take place around LDs. This study reveals a novel function of LDs in the assembly of infectious HCV and provides a new perspective on how viruses usurp cellular functions.     

Diverging effects of human recombinant anti-hepatitis C virus (HCV) antibody fragments derived from a single patient on the infectivity of a vesicular stomatitis virus/HCV pseudotype

Hepatitis C virus (HCV) is the major causative agent of blood-borne non-A, non-B hepatitis. Although a strong humoral response is detectable within a few weeks of primary infection and during viral persistence, the role played by antibodies against HCV envelope glycoproteins in controlling viral replication is still unclear. We describe how human monoclonal anti-HCV E2 antibody fragments isolated from a chronically HCV-infected patient differ sharply in their abilities to neutralize infection of HepG2 cells by a vesicular stomatitis virus pseudotype bearing HCV envelope glycoproteins. Two clones were able to neutralize the pseudotype virus at a concentration of 10 micro g/ml, while three other clones completely lacked this activity. These data can explain the lack of protection and the possibility of reinfection that occur even in the presence of a strong antiviral antibody response.     

丙型肝炎病毒蛋白作用于细胞信号转导途径的研究进展

细胞信号转导异常往往与人类疾病的发生、发展密切相关。一些病毒致病和感染机制即为病毒抗原蛋白作用宿主细胞信号转导途径,导致宿主细胞内信号转导发生紊乱。丙型肝炎病毒（HCV）是引发慢性丙型肝炎,导致肝硬化和肝细胞癌发生的主要病原体,但目前HCV的致病机制与宿主内持续感染机制尚不清楚。HCV致病机制可能与HCV表达的蛋白质干扰宿主细胞信号转导途径而导致异常的细胞信号转导有关。研究HCV蛋白对宿主细胞信号转导途径的影响不仅有助于阐明其致病机制,还能为新药设计和寻找新的治疗方法提供新思路和新靶点。本文主要综述了近年来国内外有关HCV蛋白作用细胞信号转导途径的研究进展。